Fruits, Vegetables = No Risk Reduction
For years, we have been told to eat at least five daily servings of fruits and vegetables, especially dark colored ones. Now it seems that all those vitamins and fiber have probably been good for our general health, but make not a whit of difference in cancer risk reduction. Here is an editorial by Walter Willett from Journal of the National Cancer Institute. I am including a couple of paragraphs and then a link to read more:
During the 1990s, enthusiasm swelled for increasing consumption of fruits and vegetables with the expectation that this would substantiallyreduce the risk of many cancers (1). Potential reductions as large as 50% were suggested. The National Cancer Institute's 5-A-Day program was developed in 1991 (http://dccps.nci.nih.gov/5ad_3 _origins.html) (2) to promote increasing the average consumption of fruits and vegetables to five or more servings per day, and a major line of investigation was launched to identify and isolate the phytochemicals responsible for the apparent benefits. However, the evidence for a large preventive effect of fruits and vegetables came primarily from case-control studies, which can be readily biased by differences in recall of past diet by patients with cancer and healthy control subjects. Even more problematic, participation rates in surveys have fallen sharply over the past 50 years so that those who agree to be interviewed as control subjects are likely to overrepresent health conscience persons who smoke less, exercise more, and eat more fruits and vegetables compared with those who do not participate. Because participation rates of patients with cancer, who are already in a medical system, remain high, the result is an exaggerated apparent benefit of fruits and vegetables, even if both groups report their past diets perfectly.
In summary, the findings from the EPIC cohort add further evidence that a broad effort to increase consumption of fruits and vegetables will not have a major effect on cancer incidence. Such efforts are still worthwhile because they will reduce risks of cardiovascular disease, and a small benefit for cancer remains possible. Research should focus more sharply on specific fruits and vegetables and their constituents and on earlier periods of life. For prevention of cancer, the primary focus at present should be heightened efforts to reduce smoking and obesity because obesity in the United States has become similar in magnitude to smoking as an avoidable cause.